Three quarters of the way the car traveled at a speed of V1 = 60 km / h

Three quarters of the way the car traveled at a speed of V1 = 60 km / h, the rest of the way at a speed of V2 = 80 km / h. What an average car movement.

Initial data: S1 (length of the first section of the path) = 3/4 S = 0.75S, V1 (speed on the first section) = 60 km / h; S2 (length of the second section of the path) = S – 3/4 S = 1/4 S = 0.25S; V2 (speed in the second section) = 80 km / h.

Let us define the formula for calculating the average speed: Vav = S / (t1 + t2) = S / (S1 / V1 + S2 / V2) = S / (0.75S / V1 + 0.25S / V2) = 1 / (0, 75 / V1 + 0.25 / V2).

Let’s calculate: Vav = 1 / (0.75 / 60 + 0.25 / 80) = 1 / 0.015625 = 64 km / h.

Answer: The average vehicle speed is 64 km / h.